/Engine/Source/Runtime/Engine/Classes/Engine/GameViewportClient.h
Assigns the viewport overlay widget to use for this viewport client. Should only be called when first created
void SetViewportOverlayWidget ( [TSharedPtr](API\Runtime\Core\Templates\TSharedPtr)< [SWindow](API\Runtime\SlateCore\Widgets\SWindow) > InWindow, [TSharedRef](API\Runtime\Core\Templates\TSharedRef)< [SOverlay](API\Runtime\SlateCore\Widgets\SOverlay) > InViewportOverlayWidget )